It is generally known that synthetic resins such as polyethylene, polypropylene, polyvinyl chloride, an acrylonitrile-butadiene-styrene (ABS) resin, etc., cause change of color, deterioration of mechanical strength, etc. due to heat deterioration and/or oxidation at molding or fabrication thereof and furthermore due to deterioration of weather resistance, that is, deterioration mainly by the action of ultraviolet rays and/or oxygen even after being formed into articles, and hence these articles can not endure the long use thereof.
For overcoming these faults, it is necessary to restain the occurrences of various deteriorations by adding one or more kinds of heat stabilizers or light stabilizers to the synthetic resin. As such a heat stabilizer, a combination of a phenolic compound such as tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane (Irganox 1010, trade name, made by Ciba-Geigy Aktiengesellschaft), etc., and a sulfur-series compound such as dimyristyl thiodipropionate, etc., is generally used and as such a light stabilizer, hindered amine-series compounds such as bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate (Sanol LS770, trade name, made by Sankyo Co., Ltd.) are generally known.
However, it is known that there is an antagonism between a certain kind of heat stabilizer and a certain kind of light stabilizer. When Irganox 1010 is used as a phenolic antioxidant for improving the heat resistance of a synthetic resin and simultaneously Sanol LS770 is added to the synthetic resin for improving the weather resistance, the synthetic resin having both the heat stability and the light stability can be obtained. However, when in the case of requiring more excellent heat stability, sulfur-series compound such as dimyristyl thiodipropionate, etc., which shows a synergistic effect with the phenolic compound, is additionally used for aforesaid synthetic resin, the thus obtained synthetic resin has the excellent heat stability but has the greatly reduced weather resistance. In other words, there clearly exists a phenomenon of antagonism between a hindered amine-series light stabilizer and a sulfur-series antioxidant.